The chief pilot carried sealed orders which, in the event of Japanese hostilities, directed them to keep going west around the globe until they reached the PanAm base in New York. Since PanAm didn't routinely fly this route, they had to make it up as they went along. Along the way they landed on both the Nile and Congo rivers.
History doesn't have to be dry and boring. This is not a short read but extremely well-written and gripping. I enjoyed it very much, perhaps you will too.